Bone Density Scan (cont.)
Jason C. Eck, DO, MS
Dr. Eck received a Bachelor of Science degree from the Catholic University of America in Biomedical Engineering, followed by a Master of Science degree in Biomedical Engineering from Marquette University. Following this he worked as a research engineer conducting spine biomechanics research. He then attended medical school at University of Health Sciences. He is board eligible in orthopaedic surgery.
William C. Shiel Jr., MD, FACP, FACR
Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.
In this Article
- What is osteoporosis?
- How does osteoporosis occur?
- What is "bone mineral density" (BMD)?
- Why is BMD measurement important?
- What is the relationship between BMD and fracture risk?
- Who should have BMD testing?
- How is BMD measured?
- What are other methods of measuring BMD?
- How often should DEXA scans be repeated to monitor treatment?
- What is the cost of DEXA?
- What about the accuracy of BMD testing in the doctor's office using smaller equipment?
- Summary
- Bone Density Scan At A Glance
- Find a local Rheumatologist in your town
What is "bone mineral density" (BMD)?
The absolute amount of bone as measured by bone mineral density (BMD) testing generally correlates with bone strength and its ability to bear weight. The BMD is measured with a dual energy x-ray absorptiometry test (referred to as a DEXA scan). By measuring BMD, it is possible to predict fracture risk in the same manner that measuring blood pressure can help predict the risk of stroke.
It is important to remember that BMD cannot predict the certainty of developing a fracture. It can only predict risk. It is also important to note that a bone density scan, or test, should not be confused with a bone scan, which is a nuclear medicine test in which a radioactive tracer is injected that is used to detect tumors, cancer, fractures, and infections in the bone.
The World Health Organization has developed definitions for low bone mass (osteopenia) and osteoporosis. These definitions are based on a T-score. The T-score is a measure of how dense a patient's bone is compared to a normal, healthy 30-year-old adult.
Normal: A bone BMD is considered normal if the T-score is within 1 standard deviation of the normal young adult value. Thus a T-score between 0 and -1 is considered a normal result.
Low bone mass (medically termed osteopenia): A BMD defines osteopenia as a T-score between -1 and -2.5. This signifies an increased fracture risk but does not meet the criteria for osteoporosis.
Osteoporosis: A BMD greater than 2.5 standard deviations from the normal (T score less than or equal to -2.5) defines osteoporosis.
Based on the above criteria, it is estimated that 40% of all postmenopausal Caucasian women have osteopenia and that an additional 7% have osteoporosis.
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